Reference can be had to applicant's U.S. Pat. No. 3,667,698, for Locking Seat Belt Retractor, which discloses the type of floor mounted seat belt retractor currently used in most American automobiles and over which the seat belt system of the present invention is a distinct improvement.
Seat belt retractors heretofore known and used fall into two general categories, namely, simple retractors that function only to wind up the belt and which, therefore, must be fully protracted to effectively restrain an occupant, and seat belt retractors that utilize a mechanical locking system to effect locking of the retractor at any desired point of protraction. Locking is achieved by allowing the belt to retract slightly. While the former retractor is desirable from a user's standpoint in that its spring is relatively light, it is unacceptable in view of present safety standards, since full protraction of the belt cannot be assured. The later type of locking retractor has very desirable safety characteristics, but has proved to be unacceptable to the motorist since the spring required to retract the belt concommittently drive cams, pawls and gears to energize the locking system and, therefore, is relatively heavy, tightening the belt about the user's waist to an uncomfortable degree and rendering protraction difficult. Moreover, since such known retractors lock up upon the first increment of retraction after a predetermined protraction, accidental lockup of the retractor while attempting to couple the tongue of the system into a complimentary buckle often occurs, requiring the user to allow the belt to fully retract so as to disengage the locking mechanism and thereby permit a subsequent full protraction.
The seat belt system of the present invention solves the aforementioned problems by utilizing relatively light springs to effect retraction of the seat belt and, thus, at no time present an overly tight belt to the user. Neither full protraction of the belt nor partial retraction of the belt is required since lockup, in a constructed embodiment, is controlled electrically.
When a vehicle utilizing the system of the instant invention is unoccupied, belt buildup on the retractor spool biases a locking pawl to the unlocked condition relative to a ratchet on the spool of the retractor. Upon seating of an occupant in the vehicle seat, an electromagnet is energized to hold the locking pawl of the retractor out of engagement with the ratchet thereon, permitting the seat belt to be fully protracted without the possibility of spurious lockup. After engagement of the tongue of the belt with the complimentary seat belt buckle, the energizing circuit of the electromagnet is broken, allowing the pawl on the retractor to move into engagement with its complimentary ratchet on the retractor to lock up the seat belt system. Thus, the spring of the retractor is required to be heavy enough only to retract the tongue to the storage condition. No cam, gear, or other type of mechanism is required to be operated by the retract spring of the retractor. Moreover, spurious lockup of the seat belt system is precluded since the system is deactivated until the tongue is engaged in its complimentary buckle. The system is fail safe in operation.